Emission control devices, such as diesel particulate filters (DPF), may reduce the amount of soot emissions from a diesel engine by trapping soot particles. Such devices may be regenerated during operation of an engine to decrease the amount of trapped particulate matter. Regeneration is typically achieved by raising the temperature of the DPF to a predetermined level, and ensuring that the exhaust gas entering the DPF is of a certain composition.
Diesel vehicles may further be equipped with exhaust gas recirculation (EGR) systems. EGR systems divert a portion of the exhaust gases back to the intake to cool combustion temperatures and reduce throttling losses, thus improving vehicle emissions and fuel economy. In turbocharged engines, an EGR system may include a low-pressure EGR (LP-EGR) circuit, a high-pressure EGR (HP-EGR) circuit, or both. The LP-EGR circuit diverts exhaust gases after the gases pass through the turbine of the turbocharger and injects the gases before the compressor, while the HP-EGR circuit diverts exhaust gases before the turbine and injects the gases after the intake throttle. Traditionally, the amount of LP-EGR and/or HP-EGR routed through the EGR system is measured and adjusted based on engine speed and load during engine operation to maintain desirable combustion stability of the engine while providing emissions and fuel economy benefits.
Some diesel vehicles may also be equipped with a power take-off (PTO). The power take-off is a system designed to draw power from the engine. A PTO may be connected to the transmission and equipped to drive an auxiliary drive shaft, belt, hydraulic lift or other mechanism.
It is possible for the DPF to accumulate soot when a vehicle is stationary and the engine is being used for power take-off (PTO). Conventional DPF regeneration does not occur when a vehicle is stationary and so a vehicle may be pulled out of service to be driven to perform a DPF regeneration. This has also been the case during a user commanded stationary regeneration which also requires that PTO operation stops.
The inventors have recognized the above described disadvantages and herein describe systems and method for the regeneration of a DPF without exiting a stationary PTO mode, for example as set by an operator via a selection device such as a user interface or selector switch. PTO speeds and loads tend to be steady and so higher urea dosing levels may work well to control NOx. Additionally, reducing EGR to 50% of the normal level may promote passive regeneration of the DPF.
EGR is reduced by 50% of the normal EGR level when two conditions are met. First, the DPF approaches a soot loading level at which a normal regeneration may be performed and second, the truck is in stationary PTO. To control NOx, the inventors propose to increase urea dosing. Additionally, the formation of NO2 may be affected by modifying the number of injections and the combustion phasing. In this way the DPF is regenerated during PTO by reducing EGR by 50%, or more, and NOx levels are controlled by increasing urea dosing, and/or adjusting combustion phasing and the number of fuel injections.
The systems and method described above in the present disclosure allow for regeneration of a diesel particulate filter while a vehicle is in stationary power take-off mode. Described is a method of: during select power take-off conditions, reducing an EGR rate responsive to an indication to regenerate a diesel particulate filter.
In some examples, the DPF regeneration approach during PTO operation differs from the DPF regeneration approach during non-PTO operation, such as during vehicle travel and driving operations. For example, DPF regeneration during non-PTO operation may maintain EGR rates while taking other actions to increase exhaust temperature and regenerate the DPF (e.g., adjusting injection timing, excess exhaust oxygen, etc.). As another example, the EGR rate adjustment for DPF regeneration during non-PTO operation may be to a lesser extent than for DPF regeneration during PTO operation (e.g., reducing by only 25%).
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. Further, the inventors herein have recognized the disadvantages noted herein, and do not admit them as known.